Gibbs A G, Louie A K, Ayala J A
Department of Ecology, University of California, Irvine, CA 92697, USA.
J Exp Biol. 1998 Jan;201(Pt 1):71-80. doi: 10.1242/jeb.201.1.71.
The desert fruit fly Drosophila mojavensis experiences environmental conditions of high temperature and low humidity. To understand the physiological mechanisms allowing these small insects to survive in such stressful conditions, we studied the effects of thermal acclimation on cuticular lipids and rates of water loss of adult D. mojavensis. Mean hydrocarbon chain length increased at higher temperatures, but cuticular lipid melting temperature (Tm) did not. Lipid quantity doubled in the first 14 days of adult life, but was unaffected by acclimation temperature. Despite these changes in cuticular properties, organismal rates of water loss were unaffected by either acclimation temperature or age. Owing to the smaller body size of warm-acclimated flies, D. mojavensis reared for 14 days at 33 degrees C lost water more rapidly on a mass-specific basis than flies acclimated to 25 degrees C or 17 degrees C. Thus, apparently adaptive changes in cuticular lipids do not necessarily result in reduced rates of water loss. Avoidance of high temperatures and desiccating conditions is more likely to contribute to survival in nature than changes in water balance mediated by surface lipids.
沙漠果蝇（Drosophila mojavensis）会经历高温和低湿度的环境条件。为了了解这些小昆虫在如此恶劣条件下生存的生理机制，我们研究了热驯化对成年沙漠果蝇表皮脂质和水分流失速率的影响。在较高温度下，平均碳氢链长度增加，但表皮脂质的熔点（Tm）没有变化。脂质含量在成虫生命的前14天增加了一倍，但不受驯化温度的影响。尽管表皮特性发生了这些变化，但水分流失的机体速率不受驯化温度或年龄的影响。由于热驯化果蝇的体型较小，在33摄氏度下饲养14天的沙漠果蝇按质量比计算比适应25摄氏度或17摄氏度的果蝇失水更快。因此，表皮脂质的明显适应性变化不一定会导致水分流失速率降低。与由表面脂质介导的水分平衡变化相比，避免高温和干燥条件更有可能有助于在自然环境中生存。
